ABSTRACT: What lies on the two sides of the linguistic
divide is fairly clear: On one side, you have organisms buffeted about
to varying degrees, depending on their degree of autonomy and plasticity,
by the states of affairs in the world they live in. On the other side,
you have organisms capable of describing and explaining the states of affairs
in the world they live in. Language is what distinguishes one side from
the other. How did we get here from there? In principle, one can tell a
seamless story about how inborn, involuntary communicative signals and
voluntary instrumental praxis could have been shaped gradually, through
feedback from their consequences, first into analog pantomime with communicative
intent, and then into arbitrary category names combined into all-powerful,
truth-value-bearing propositions, freed from the iconic "shape" of their
referents and able to tell all. The attendant increase in speed and scope
in acquiring and sharing information can be demonstrated in simple artificial
life simulations that place the old and new means into direct competition:
Symbolic theft always beats sensorimotor toil, and the strategy is evolutionarily
stable, as long as the bottom-level categories are grounded in sensorimotor
toil.

If you have a preference for "hard evidence" you approach the problem
of language origins at your own peril. It has been suggested that language
is a kind of organ (Chomsky 1972; Pinker & Bloom 1990), but even if
it is, it must share the fate of that other organ of which any language
organ is surely only a part, the brain, namely, that it leaves no trace
after its demise, or at least no trace that anyone has yet given a convincing
functional (let alone cognitive) interpretation (Holloway 1970, Wilkins
& Wakefield 1995).

So in pondering the origins of the language organ, we cannot expect
much help from the fossil record. But if soft organs deny us hard evidence,
surely their behavioral functions are even more evanescent: "Verba volunt,
Scripta manent," to be sure, but writing surely arrived on the scene too
late in the day to help us (Harnad 1991).

Some have turned, in desperation, to other traces: tools, weapons, drawings
(Isaac 1987). They have hypothesised that either language was necessary
to make and/or use these artifacts or that there is some formal or functional
commonality or co-dependency between the capacity to make or use them and
the capacity to speak. But hypotheses are hardly evidence, let alone hard
evidence, and in and of themselves, artifacts are just artifacts.

Others have looked to contemporary species, rather than ancient ones,
for a clue (Greenfield 1992), but hunting and tool-making and -use can
hardly be said to be garrulous activities today, so they are not very compelling
evidence for loquacity, let alone its origins, long ago. Moreover, contemporary
evidence for rudimentary tool-making and use in animals that have neither
language nor the ability to acquire it goes against the idea that these
functions have much in common.

The other prominent functional commonality that has been proposed is
between language and consciousness (Rolls 1997, 2000). Some have thought
language was a prerequisite for consciousness; but if this were true, it
would deny pain to all creatures who were incapable of expressing it in
words, and surely that's wrong, although, again, there is no "hard" evidence
for it, short of being the mute animal feeling the pain (Harnad
2000).

The impossibility of determining empirically whether or not a non-speaking
creature is conscious -- otherwise known as the "other minds" problem --
does suggest one genuine point of commonality with the problem of language
origins, however: Consider the problem of "demoting" explanations, when
you try to attribute consciousness to an animal or a machine: You can always
interpret a system "as if" it were conscious, even an inert, nonbehaving
system like a book on a table. You can say the book knows it's on the table,
wants to be on the table, etc. Who's to say otherwise? The data are perfectly
compatible with that interpretation, it's just that the interpretation
seems both unnecessary and wrong. We can understand the book's being on
the table without having to infer that it is conscious. If anyone claims
the consciousness is necessary, we can ask why? There is no physical reason
why a book needs to know it's on a table in order to be on a table.

Demoting conscious interpretations of inert systems is trivial. It's
only a bit harder to demote dynamic, performing systems: Physics and engineering
do not require, nor can they use, a conscious explanation of the functioning
of a thermostat ("it feels hot," "it wants to turn off the furnace") or
a car, an airplane or a computer. The performance of each of these systems
is fully explained by mindless mechanisms.

The trick is to show where the need for a conscious explanation kicks
in: What functional capacity cannot be explained without recourse
to consciousness? Behaviour-analytic psychology gave us operant and Pavlovian
conditioning, but do these require consciousness? It is easy to build devices,
not very different from thermostats, whose performance is shaped by their
history of associations or their history of reinforcements, especially
in this era of neural nets and other computational models. So any behavior
that can be reduced to an operant or a Pavlovian explanation has been demoted
to a mindless explanation.

And no behavior seems to be immune to this sort of demotion: Show me
a creature, human or nonhuman, that you think is managing to do something
only with the aid of consciousness and it will invariably be easy to show
that the same thing could be accomplished by a mindless mechanism merely
shaped by the consequences of its behavior, just as Skinner would have
said: Gorillas rubbing off from their foreheads yellow spots that they
have seen in their mirror image (Gallup 1970)? All the data are there for
a mindless learning mechanism to learn that correlation from the sensorimotor
interactions with its mirror image: Happens too fast? Well then the same
correlation, or a generalization of it, could have been "prepared" by evolution,
likewise a mindless process.

The point is not to deny that gorillas are conscious and do recognize
themselves in the mirror. It is the causal role of the consciousness in
the explanation that keeps on turning out to be unnecessary, hence the
demotion: The rule seems to be, whatever we happen to do mindfully, could
just as well have been done mindlessly.

Now this is not a conference on the origin of consciousness. I have
only introduced the ever-ready, mindless demoting explanation by way of
analogy, for it has an exact counterpart in the case of language. Here
is the heart of the analogy: Just as it is impossible to show that THIS
is where what you can do with a mindless mechanism ends, and beyond this
you can only go with a mind -- there is no such point, and hence no functional
explanation for why consciousness should ever kick in (though it certainly
does) -- there is likewise no point at which nonlinguistic praxis and pantomime
end and linguistic propositions take over.

Let's define terms. "Praxis" just refers to our sensorimotor skills,
the things we and other species need to be able to do in order to live
and act out our lives: Finding food, eliminating wastes, avoiding predators,
finding mates, etc., each according to the demands of our own species-specific
niche. Nonlinguistic creatures share this nonverbal portion of our praxic
repertoires (including the capacity to learn by operant and Pavlovian conditioning),
and that covers a lot.

"Pantomime" is a special subset of praxis: It is social. Behavioral
imitation (as opposed to anatomical mimicry) largely occurs between living
creatures, not between living creatures and inert objects (Byrne &
Russon 1998). But pantomime includes both automatic and deliberate imitation.
A songbird may imitate the tune of its conspecifics mindlessly (who knows),
but people at least, and perhaps other species as well, can "act out" in
ways that are intended to get you to do and even think something. We know
this in the case of people (I might cover my mouth and point when I mean
for you to know that someone else is present), but we know from the demoting
explanation of gorilla mirror-recognition that even pantomime can be explained
as mindlessly as any other form of praxis.

So far, this is not the analogy I was promising; it is still the problem
of consciousness. To appreciate the analogy, we first have to pass from
pantomime to propositions. A few critical differences have to be borne
in mind: A pantomime, like a picture, cannot be true or false. It can only
be more or less like whatever it is a picture or pantomime of. Praxic gestures,
whether pantomimic or just plain instrumental acts (Catania & Harnad
1988; Harnad 1996b), do not have truth values. They can of course be construed
as
having truth values, but then they are construed as propositions. Propositions
propose something. That's why they have truth values: What they claim or
propose to be the case may or may not be the case. If not, then they are
false.

Now when I put my hand on my mouth and pointed, you could have construed
that as the proposition "There is someone else in the room," and, if upon
inspection, it turned out there was no one else in the room, you might
want to say I had lied (Whiten & Byrne 1988). But in a court of law,
so accused, I could claim that all I had done was put my hand on my mouth
and pointed. I had never said -- never uttered a verbal contract -- to
the effect that there was someone in the room. That was just your interpretation.
I was merely performing a pantomime. I never intended you to construe it
as a proposition.

By way of contrast, if I were in a crowded theater and I yelled "Fire,"
I could be held liable for causing a stampede and causing injury if it
turned out I had been crying wolf. It would not do me much good to claim
(though it might be true) that I had merely been saying out loud words
that rhymed with "dire," and that I had not intended it to be construed
as a proposition. If this distinction sounds legalistic rather than objective
and empirical, then you are beginning to catch my drift, but there is nevertheless
a way, if not to draw the line, then to make the nonpropositional construal
more and more improbable:

"Fire" uttered in isolation is, by accepted social convention, a shorthand
way of uttering the proposition (say) "There is a fire in here." It is
true that one might have been enumerating the words that rhyme with "dire,"
but that is unlikely, and if it is unlikely for a monosyllabic proposition
like "fire," it is still more unlikely for the longhand version "There
is a fire in here." As the utterance becomes more complex, it becomes more
far-fetched to construe it in any other way than propositionally.

So with complex propositions, we are in a performance domain that is
radically different from praxis and pantomime, for propositions DO have
truth value. Moreover, they seem to have the power to express any truth:
This hypothesis, in the form of the "effability" hypothesis, to the effect
that anything that is the case can be described in words, was put forward
by Jerry Katz (1976) in the NY Academy of Sciences Conference that helped
re-open the language origins question in our century. In the same volume,
an independent variant of the effability hypothesis was proposed by Steklis
and Harnad (1976) in the form of the "translatability" criterion, to the
effect that all natural languages are fully intertranslatable. That turns
out to be logically equivalent to the effability hypothesis, but it may
be the more suggestive version for our purposes here, because it highlights
the "cryptographic" aspects of language's expressive power: There are of
course a limitless number of propositions, but every language has at least
one way of expressing them all: What are the chances of coming out with
just the right string of symbols, but without intending that proposition?
They quickly approach the chances of chimpanzees typing a passage from
Shakespeare (Harnad 1996a).

So here we are faced with a profound divide: One one side, is the world
of praxis, with its objects, events and states of affairs. It has some
limited resources for aping itself: I can try to draw or imitate a tree
in the wind or perhaps even a rainbow over a horizon. But my praxic repertoire
quickly runs out of resources in relation to all the objects and events
and states there are in the world: How to mime that "all men are mortal,"
or that "a continuous function is everywhere differentiable?" Those are
states of affairs that can only be described in words. Moreover, as I suggested
before, even pictures and mime are not descriptions: they are merely
other states of affairs that happen to have some similarity to whatever
they are pictures of. So even to construe pantomime as anything other than
"being there" -- like a poem, that should not "mean" but "be" -- is already
to construe it propositionally.

And here is where the analogy with the demotion of consciousness comes
in: For case by case, practically, or rather praxically speaking, every
instance of praxis and pantomime could be acted on instrumentally: The
person who covers his mouth and points could be a correlate and hence a
predictor, like the yellow spot on the gorilla's forehead, of the presence
of someone else in the room. I need not have recourse to a proposition
for that; hence a propositional construal need not be posited for the pantomime
itself. Where does the proposition need to kick in? And in what does its
kicking in consist? What can we do with language that we can't do with
praxis and pantomime?

Candidates immediately come to mind: It's hard to mime things that one
does not have the equipment to depict. It's hard to mime in the dark. In
their presence, we can point to objects we'd have trouble mimicking, but
in their absence? It's hard to mime either/or relations, or conditional
relations -- hard to mime relations themselves, or features or properties.
The more abstract something is, the harder it is to mime it, because miming
is concrete and particular.

Can we even mime kinds, as opposed to specific instances? We've
conceded that the proposition "All men are mortal" might defy miming, but
could we even mime "mortal"? Sure, we can show someone or something dying;
and then maybe show another, entirely different thing dying, and hope that
in providing this panorama of concrete instances, the abstract category
will somehow be picked out. But how would we mark that abstract
category that we had laboriously acted out? And how would we carry it into
the more complex proposition "I am mortal," much less "All men are mortal."
Be careful to distinguish "I am going to die," which is relatively easy
to mime, from "I am mortal," which is not.

So we need to be able to mark abstract categories, such as "mortal."
At the very least, one of the concrete depictions of some dying creature
would have to do double duty for that dying creature, and for mortality
in general. Now notice that for its concrete role of depicting a particular
dying creature, the resemblance between the depiction and the object depicted
is the kind of nonarbitrary, analog relation that psychologists have called
"iconic." Saussure stressed the arbitrariness of linguistic signs, in contrast
to this. Why? I'm not sure whether Saussure intuited the property that
Jorge-Luis Borges (1969) singled out in his "Funes the Memorious."

Funes was a man who once fell off a horse and after that time he could
never forget anything. He had an infinite rote memory for every concrete
particular he ever encountered. His memory was so good that he gave all
the integers unique proper names -- Fred, Jeff, Charlie -- all the way
up into the hundreds of thousands till he got bored. Yet he had the greatest
difficulty understanding why the rest of us, ordinary mortals with frail
memories, insisted on calling (what we referred to as) that dog "Fido"
in that particular position at that particular instant by the same name
as what we insisted was the same dog, "Fido" at another instant, in another
position. For to Funes, these were all infinitely unique and different
experiences. His memory faithfully mimed and saved them all. What it couldn't
do was forget or ignore any of it. Hence it could not abstract. Hence he
couldn't mark all those instances of "Fido" with the arbitrary sign "Fido."
They were all infinitely different and unique to him. So of course if Borges
had been completely consistent, he could not have portrayed Funes as speaking
at all, for to speak he would have had to have gained a command of those
arbitrary names for abstract categories that would have required forgetting
or ignoring all the differences that are preserved in a faithful copy.
Instead, all he had was the nonarbitrary icons, each unique to its specific
instance (Harnad 1987).

Now of course it's not just a speaking Funes that is impossible; even
a nonverbal Funes could not survive for a day if he could not abstract.
The abstraction would not have to be marked by an arbitrary sign; it could
be marked by a nonarbitrary praxic response such as sitting only on those
things that afforded sitability-upon, and so on. A repertoire of evolutionarily
prepared as well as learned feature detectors that subserved praxis would
serve creatures nearly as complex and capable as ourselves quite adequately.
Where does the added power of the arbitrary sign and the proposition kick
in? What can species not do by praxis and pantomime alone?

My main objective here was to suggest that this is the real question
at the heart of the problem of the origin of language. The origin of language
is the origin of marking categories with arbitrary "signs" (symbols) and
stringing those symbols together into decsriptive propositions that far
outstrip the possibilities of praxis and pantomime. What would be the survival
value, the adaptive advantage, of propositions over mere praxis and pantomime?

In a series of artificial life simulations (Cangelosi & Harnad 2000;
Cangelosi, Greco & Harnad 2000) we have tried to show that this advantage
can be thought of as the advantage of (symbolic/propositional) "theft"
over honest (sensorimotor) "toil." I will close with a sketch of how this
would work. "Honest toil" is good old trial-and-error operant learning
guided by feedback from the consequences of one's behaviour, as in learning
to distinguish edible mushrooms from toadstools: An organism samples mushrooms,
tastes them, see whether it gets sick or gets nourished by them, and eventually,
if the category is learnable, learns to tell apart the ones that afford
nourishment from the ones that are toxic. Those are categories an orgamism
has earned by honest toil.

Note that the foregoing is just a description, not an explanation. An
explanation requires a causal mechanism for HOW the organism managed to
learn to tell apart edible and toxic mushrooms by honest toil: how its
brain managed to find the critical features that reliably distinguish the
shadows cast on its senses by mushrooms from those cast by toadstools.

Neural nets are one natural candidate for such a feature-detecting,
category-learning mechanism (Tijsseling & Harnad 1997). Mushroom-sorting
(Cangelosi & Paris 1988) is of course not a realistic paradigm for
category learning; it is just a "toy" problem. (For one thing, the timing
is unrealistic: If telling apart mushrooms and toadstools were hard, then
how could a creature in a mushroom world afford to sample them by trial
error long enough to learn which kinds are which without starving itself
to death?)

But contrast this with the inborn internal feature detectors of the
frog, who already "knows" what kind of thing to flick his tongue out at
from birth, or rather, from the time of metamorphosing from a tadpole into
an air-breathing frog. Let us say that the frog has come by his bug-detectors
not by honest toil, as in the case of the hypothetical mushroom-detectors,
but by Darwinian theft: He was born with already prepared detectors; he
got them "for free." Of course this too leaves out the critical part, for
nothing comes for free. If the frog did not perform the honest toil, involving
variation and selection on the basis of the consequences of trial and error,
then the "Blind Watchmaker (evolution by natural selection) must have done
it for him.

But it is not Darwinian theft that I meant when I spoke of the virtues
of theft over honest toil. To understand what form of theft I had in mind,
we have to go back to the mushroom world: Suppose the bleaker scenario
I mentioned were the actual one: Suppose there was not enough time in the
day to sample toadstools and mushrooms until you had them safely sorted
out: If you had to rely on honest toil alone, you stood a good chance of
starving to death or perhaps getting poisoned. But suppose there were others
of your kind who already had the detectors (by some means or other): If
they could just describe to you in words the features of the safe
and unsafe mushrooms, perhaps supplemented with some pointing to examples,
they could save you an awful lot of honest toil. (Biederman & Shiffrar
[1987] have provided evidence that a verbal description of the winning
features, together with some good examples, can fast-forward a novice to
90% of grandmaster performance level in newborn chicken-sexing, a level
that normally requires months of honest toil at the feet of black-belted
masters.)

Now notice that in a realistic scenario "theft" is a misnomer here,
for, all else being equal, symbolic theft (hearsay) is a victimless crime.
If you know something I don't, you are not in general any the poorer for
telling me about it and saving me the time and trouble of learning it the
hard way. Of course, we have managed to put a price tag on everything,
and perhaps in is only in our contemporary information society that this
kind of "gift" (as opposed to theft) is becoming the commerce it
was always destined to be, but gift, barter, theft, commerce or reciprocal
altruism, it is clear that it is language that has conferred on us the
power of bypassing countless hours of honest toil.

Cangelosi & Parisi (1988) tried to show the adaptive advantages
of symbolic theft in artificial life simulations. They put the theft/toil
strategies into competition: A population of virtual mushroom-foragers
(back-propagation nets) learned to distinguish edible from inedible the
hard way, through trial-and-error sensorimotor toil, supervised by feedback
from errors; another population learned it the easy way, by overhearing
the toilers vocalize "edible" and "inedible." The thieves did not have
to learn the features, because the toilers had already done it for them.
And there were plenty of mushrooms, so vocalizing freely did not deprive
anyone of anything. Within a few generations the thieves were out-surviving
and out-reproducing the toilers. The theft strategy defeated the toil strategy,
and demonstrated the adaptive advantage of language.

Or did it? Would such a strategy be "evolutionarily stable," or would
it, like certain forms of cheating and parasitism, eventually play itself
out? For consider that the theft strategy only works while there are toilers
in the know within earshot; without the guidance of hearsay, the thief
is lost, not having learned the critical features. So if anything, a competition
of this sort, continued across generations, could at best induce an oscillation,
with thieves at an advantage over toilers while there are plenty of toilers
about, vocalizing their hard-won knowledge, but as the toilers' numbers
shrink in favour of the thieves, the thieves become increasingly clueless
and their own numbers accordingly shrink in favour of the toilers.

Such an oscillation is evolutionarily possible, but there is certainly
no evidence of it today: We are all thieves. How did this come to pass?
Theft is parasitic on toil: it is "ungrounded" (Harnad 1987, 1990) unless
there are toilers about too. So perhaps we all do the groundwork, acquiring
certain "basic" categories the old way, by direct sensorimotor toil, and
then the rest can be acquired the new way, by the Biederman/Shiffrar strategy
of symbolic description, stringing together the grounded names of the basic
categories into propositions describing higher-order categories by Boolean
combinations (Harnad 1996a). This is indeed what our mushroom-simulations
have shown (Cangelosi & Harnad 2000): Everyone learned the ground-level
categories by toil, but for higher-order categories, the theft strategy
beats the toil stratgey, and it is evolutionarily stable.

This is still a toy simulation, however; it remains to be seen whether
this model for the dapative advantage of language will scale up to lifesize
ecological settings.